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STRUCTURED COMPARISON
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STRUCTURED COMPARISON
Choose two categories from the same family. The same properties, equal visual weight, sources next to the claims they support.
Cookware
The material is iron, and during cooking some of it passes into the contents. The amount has been measured and modelled: it rises with temperature and time and rises markedly as pH falls. The World Health Organization has identified iron cookware as a potential strategy against iron deficiency anaemia.
The release of iron itself has been measured and modelled. The consequence for people remains uncertain: in a systematic review of thirteen studies a significant rise in haemoglobin was reported in four, with only a minor rise in the rest, and the authors state plainly that the approach needs further research.
The work this side rests on examines several kinds of iron cookware and singles out nitrided pots as the most widely used, building the kinetics of iron release for them. The platform gives no separately measured description of cast iron as an alloy: no suitable source was found.
On 316L steel, what is usually only described has been measured: the protective film is bi-layered, and the share of chromium and molybdenum within it grows. The measurement avoided any contact with air during transfer, so the film was studied as it had formed in solution.
Iron release rises with higher temperature, longer cooking, lower pH and in the presence of acetic acid. The work did not stop at observation: kinetic models were built to predict release by temperature and by pH.
Most is released from new cookware; with each successive cooking cycle release falls and settles at a steady level after roughly the sixth. Long cooking increases release: over 20 hours nickel rose 34-fold and chromium about 35-fold relative to sauce cooked without steel. Different grades of steel give different amounts.
The transfer of iron from the pan into the food has been measured, and it is the basis of the proposal to use iron cookware against iron deficiency anaemia. A systematic review of thirteen studies reports improvement in the iron content of food and in its bioavailability.
The World Health Organization has identified the use of iron cookware as a potential measure against iron deficiency anaemia and pointed to a shortage of action-oriented research in the area. This is a position on where work should go, not a permission or a limit: the platform cites no separate standard for iron from cookware.
The 2020 agency assessment sets a tolerable daily intake of nickel at 13 µg per kilogram of body weight; for the acute effect in nickel-sensitised people the figure given is 4.3 µg per kilogram. The figures apply to nickel from ALL dietary sources, not from cookware alone.
Counted for this table only, not for the whole site.
Plastic particles in the food
In the experiment it added none: non-plastic cookware introduced no microplastics
Both sides are compared on one measurable feature: what the pan adds to the food. Cast iron releases iron, and the amount has been measured and modelled by temperature, time and acidity; the consequence for people remains uncertain — a significant rise in haemoglobin was reported in four studies out of thirteen. Stainless steel releases nickel and chromium, most of all when new and in acid, and the release figures come from a single work that is more than ten years old. An agency reference for nickel makes those amounts judgeable. The differences here describe what ends up in the food.
FREQUENTLY EXPLORED
The resistance comes not from the iron but from a chromium-enriched oxide film on the surface — shown by direct surface measurements on 316L food-grade steel. The film is not absolute: in an acidic medium nickel and chromium pass from the steel into the food.
All the figures for nickel and chromium release come from one work, and it is more than ten years old — the platform marks it as stale. No later measurements of the same subject were found. The reference against which those figures are judged is, by contrast, current: the 2020 agency assessment rests on more than 47,000 occurrence measurements.
In measurements on tomato sauce, nickel concentrations rose up to 26-fold and chromium up to 7-fold after six hours of cooking, depending on the grade of steel. At the tenth cooking cycle an average of 88 µg of nickel and 86 µg of chromium passed into a 126 g serving of sauce. The agency assessment names systemic contact dermatitis in nickel-sensitised people as the critical acute effect.
The same measured zero for cookware without a plastic coating. The same caveat: the work divides cookware into plastic and non-plastic and does not single out cast iron.
In the same experiment non-plastic cookware introduced no microplastics into the food simulant at all — a measured zero, not an absence of data. The caveat: the work divides cookware into plastic and non-plastic and does not name a particular grade of steel.
Evidence reviewed: September 3, 2026
Sources are reviewed by the CONTRAST editorial team. External links open in a new tab.